Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932420AbcDZXhW (ORCPT ); Tue, 26 Apr 2016 19:37:22 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41338 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755001AbcDZXhT (ORCPT ); Tue, 26 Apr 2016 19:37:19 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Hangbin Liu" , "YOSHIFUJI Hideaki" , "David S. Miller" Date: Wed, 27 Apr 2016 01:02:24 +0200 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 095/115] net/ipv6: add sysctl option accept_ra_min_hop_limit In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8426:ae4:c500:9cba:69ae:962d:6167 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4727 Lines: 137 3.2.80-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Hangbin Liu [ Upstream commit 8013d1d7eafb0589ca766db6b74026f76b7f5cb4 ] Commit 6fd99094de2b ("ipv6: Don't reduce hop limit for an interface") disabled accept hop limit from RA if it is smaller than the current hop limit for security stuff. But this behavior kind of break the RFC definition. RFC 4861, 6.3.4. Processing Received Router Advertisements A Router Advertisement field (e.g., Cur Hop Limit, Reachable Time, and Retrans Timer) may contain a value denoting that it is unspecified. In such cases, the parameter should be ignored and the host should continue using whatever value it is already using. If the received Cur Hop Limit value is non-zero, the host SHOULD set its CurHopLimit variable to the received value. So add sysctl option accept_ra_min_hop_limit to let user choose the minimum hop limit value they can accept from RA. And set default to 1 to meet RFC standards. Signed-off-by: Hangbin Liu Acked-by: YOSHIFUJI Hideaki Signed-off-by: David S. Miller [bwh: Backported to 3.2: - Adjust filename, context - Number DEVCONF enumerators explicitly to match upstream] Signed-off-by: Ben Hutchings --- --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -1070,6 +1070,14 @@ accept_ra_defrtr - BOOLEAN Functional default: enabled if accept_ra is enabled. disabled if accept_ra is disabled. +accept_ra_min_hop_limit - INTEGER + Minimum hop limit Information in Router Advertisement. + + Hop limit Information in Router Advertisement less than this + variable shall be ignored. + + Default: 1 + accept_ra_pinfo - BOOLEAN Learn Prefix Information in Router Advertisement. --- a/include/linux/ipv6.h +++ b/include/linux/ipv6.h @@ -153,6 +153,7 @@ struct ipv6_devconf { #endif __s32 max_addresses; __s32 accept_ra_defrtr; + __s32 accept_ra_min_hop_limit; __s32 accept_ra_pinfo; #ifdef CONFIG_IPV6_ROUTER_PREF __s32 accept_ra_rtr_pref; @@ -213,6 +214,8 @@ enum { DEVCONF_DISABLE_IPV6, DEVCONF_ACCEPT_DAD, DEVCONF_FORCE_TLLAO, + DEVCONF_USE_OIF_ADDRS_ONLY = 37, + DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT, DEVCONF_MAX }; --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -185,6 +185,7 @@ static struct ipv6_devconf ipv6_devconf #endif .max_addresses = IPV6_MAX_ADDRESSES, .accept_ra_defrtr = 1, + .accept_ra_min_hop_limit= 1, .accept_ra_pinfo = 1, #ifdef CONFIG_IPV6_ROUTER_PREF .accept_ra_rtr_pref = 1, @@ -219,6 +220,7 @@ static struct ipv6_devconf ipv6_devconf_ #endif .max_addresses = IPV6_MAX_ADDRESSES, .accept_ra_defrtr = 1, + .accept_ra_min_hop_limit= 1, .accept_ra_pinfo = 1, #ifdef CONFIG_IPV6_ROUTER_PREF .accept_ra_rtr_pref = 1, @@ -3943,6 +3945,7 @@ static inline void ipv6_store_devconf(st #endif array[DEVCONF_MAX_ADDRESSES] = cnf->max_addresses; array[DEVCONF_ACCEPT_RA_DEFRTR] = cnf->accept_ra_defrtr; + array[DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT] = cnf->accept_ra_min_hop_limit; array[DEVCONF_ACCEPT_RA_PINFO] = cnf->accept_ra_pinfo; #ifdef CONFIG_IPV6_ROUTER_PREF array[DEVCONF_ACCEPT_RA_RTR_PREF] = cnf->accept_ra_rtr_pref; @@ -4544,6 +4547,13 @@ static struct addrconf_sysctl_table .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, + }, + { + .procname = "accept_ra_min_hop_limit", + .data = &ipv6_devconf.accept_ra_min_hop_limit, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, }, { .procname = "accept_ra_pinfo", --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1276,18 +1276,16 @@ static void ndisc_router_discovery(struc if (rt) rt->rt6i_expires = jiffies + (HZ * lifetime); - if (ra_msg->icmph.icmp6_hop_limit) { - /* Only set hop_limit on the interface if it is higher than - * the current hop_limit. - */ - if (in6_dev->cnf.hop_limit < ra_msg->icmph.icmp6_hop_limit) { + if (in6_dev->cnf.accept_ra_min_hop_limit < 256 && + ra_msg->icmph.icmp6_hop_limit) { + if (in6_dev->cnf.accept_ra_min_hop_limit <= ra_msg->icmph.icmp6_hop_limit) { in6_dev->cnf.hop_limit = ra_msg->icmph.icmp6_hop_limit; + if (rt) + dst_metric_set(&rt->dst, RTAX_HOPLIMIT, + ra_msg->icmph.icmp6_hop_limit); } else { - ND_PRINTK2(KERN_WARNING "RA: Got route advertisement with lower hop_limit than current\n"); + ND_PRINTK2(KERN_WARNING "RA: Got route advertisement with lower hop_limit than minimum\n"); } - if (rt) - dst_metric_set(&rt->dst, RTAX_HOPLIMIT, - ra_msg->icmph.icmp6_hop_limit); } skip_defrtr: